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A rare lymphoma that grows as fluid rather than as a lump: it fills the space around the lungs, the heart or the bowel without forming a mass. It is caused by Kaposi sarcoma herpesvirus and arises mostly in people with advanced HIV infection, and it is diagnosed by sending the fluid itself for testing.
What it is. A large B-cell lymphoma driven by Kaposi sarcoma herpesvirus, also called human herpesvirus 8, the same virus that causes Kaposi sarcoma. The lymphoma cells float free in a body cavity and produce fluid: a pleural effusion around the lung, a pericardial effusion around the heart, or ascites in the abdomen. Classically there is no tumour mass at all, which is why the diagnosis is made on the fluid.
How it differs from the lymphomas around it. WHO-HAEM5 groups it in a family of conditions caused by the same virus: multicentric Castleman disease, germinotropic lymphoproliferative disorder, primary effusion lymphoma, its extracavitary form, and KSHV/HHV8-positive diffuse large B-cell lymphoma. The classification acknowledges that the boundaries between them are not clean, that individual patients overlap, and that difficult cases should be settled in a multidisciplinary meeting rather than by rule. In particular, telling a lymph node-based extracavitary primary effusion lymphoma from a KSHV/HHV8-positive diffuse large B-cell lymphoma can be arbitrary; the International Consensus Classification prefers the latter diagnosis where Epstein-Barr virus is negative and the tumour expresses IgM lambda.
The lymphoma it is most often confused with, and the 2022 change that separates them. There is a second disease that also presents as lymphoma confined to a body cavity, in older people without immune deficiency who have heart failure, kidney failure or cirrhosis causing fluid to accumulate. It is not caused by Kaposi sarcoma herpesvirus, its cells look like ordinary mature B cells rather than plasmablasts, and it behaves considerably better. WHO-HAEM5 made it a separate entity in 2022, calling it fluid overload-associated large B-cell lymphoma; the International Consensus Classification calls it primary effusion-based lymphoma that is negative for both viruses, and lists it as provisional. Distinguishing the two matters because the outlook is different.
Who gets it. Most often a person with advanced, often undiagnosed, HIV infection; it also occurs after organ transplant and in older people from regions where Kaposi sarcoma herpesvirus is common, including parts of the Mediterranean and sub-Saharan Africa. In people with HIV the tumour usually carries Epstein-Barr virus as well; in older HIV-negative people it usually does not.
How it is diagnosed and treated. The fluid is drained and sent for cell counts, cytology, flow cytometry and immunohistochemistry or in situ hybridisation for the virus. The cells are large and plasmablastic, usually lacking the B-cell markers (CD20 is typically negative) and carrying plasma cell markers instead, which is why anti-CD20 antibodies have no role. Treatment is combination chemotherapy together with full antiretroviral therapy where there is HIV; the regimens, which have never been compared in a randomised trial, sit in the treatment layer of this family and on the HIV-associated lymphoma page.
In the United States, 236 adults were recorded in the SEER registries between 2001 and 2021, with a median age of 51 years and 88 per cent of them men. The age-adjusted incidence rose from 1.0 to 1.6 cases per ten million person-years between the first and second halves of that period. Five-year relative survival improved from 21 to 37 per cent across the same two periods, and median overall survival from 4 to 12 months, which the authors attribute to advances in both lymphoma treatment and HIV care.
Leukaemias, myeloma and MDS live in the marrow and blood; lymphomas grow in lymph nodes and spleen. The node stations are the disease map, not a route of spread, and staging counts them.
In lymphoma the node stations are the disease itself; staging (Ann Arbor / Lugano) counts how many regions and sides of the diaphragm are involved.
Same organ: High-grade B-cell lymphoma with MYC and BCL2 rearrangements (double-hit lymphoma), Mediastinal grey zone lymphoma, Plasmablastic lymphoma, T-cell/histiocyte-rich large B-cell lymphoma, EBV-positive diffuse large B-cell lymphoma, Primary large B-cell lymphoma of the testis, Gastric MALT lymphoma, Ocular adnexal MALT lymphoma, Extranodal NK/T-cell lymphoma, Adult T-cell leukaemia/lymphoma, ALK-positive anaplastic large cell lymphoma, ALK-negative anaplastic large cell lymphoma, Breast implant-associated anaplastic large cell lymphoma, Primary cutaneous anaplastic large cell lymphoma, Lymphomatoid papulosis, Mycosis fungoides, Enteropathy-associated T-cell lymphoma, Monomorphic epitheliotropic intestinal T-cell lymphoma, Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), Splenic marginal zone lymphoma, Nodal marginal zone lymphoma, Primary cutaneous marginal zone lymphoma, Primary cutaneous follicle centre lymphoma, Sezary syndrome, Nodal T-follicular helper cell lymphoma, angioimmunoblastic type (angioimmunoblastic T-cell lymphoma), Hepatosplenic T-cell lymphoma, Intravascular large B-cell lymphoma, Lymphomatoid granulomatosis, T-cell prolymphocytic leukaemia, Splenic B-cell lymphoma/leukaemia with prominent nucleoli (formerly B-cell prolymphocytic leukaemia and hairy cell leukaemia variant), T-cell large granular lymphocytic leukaemia, Mixed-phenotype acute leukaemia, Myeloid leukaemia of Down syndrome, Burkitt leukaemia, Marginal zone lymphoma, Cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome), Primary mediastinal (thymic) large B-cell lymphoma, Leukaemia (all types), Acute myeloid leukaemia, Acute lymphoblastic leukaemia, Chronic lymphocytic leukaemia, Chronic myeloid leukaemia (CML), Diffuse large B-cell lymphoma, Follicular lymphoma, Hodgkin lymphoma, Mantle cell lymphoma, Multiple myeloma, Non-Hodgkin lymphoma (all types), Myelodysplastic syndromes / neoplasms (MDS), Myeloproliferative neoplasms (PV, ET, myelofibrosis), Polycythaemia vera (PV), Essential thrombocythaemia (ET), Waldenström macroglobulinaemia, Hairy cell leukaemia, Peripheral T-cell lymphomas (including cutaneous T-cell lymphoma), Blastic plasmacytoid dendritic cell neoplasm (BPDCN), Burkitt lymphoma, HIV-associated (AIDS-related) lymphomas, Chronic myelomonocytic leukaemia and MDS/MPN overlap neoplasms, Systemic mastocytosis, Erdheim-Chester disease, Rosai-Dorfman disease and other histiocytic neoplasms, Langerhans cell histiocytosis (LCH), Post-transplant lymphoproliferative disorder (PTLD), FLT3-mutated acute myeloid leukaemia, IDH1- and IDH2-mutated acute myeloid leukaemia, NPM1-mutated and KMT2A-rearranged acute myeloid leukaemia, Secondary and therapy-related acute myeloid leukaemia, Acute promyelocytic leukaemia, Acute myeloid leukaemia in older or unfit patients, Smouldering multiple myeloma, Newly diagnosed multiple myeloma, transplant-eligible, Newly diagnosed multiple myeloma, transplant-ineligible, Relapsed or refractory multiple myeloma, Plasma cell leukaemia, Lower-risk myelodysplastic syndromes, Higher-risk myelodysplastic syndromes, Chronic lymphocytic leukaemia, first treatment, Relapsed or refractory chronic lymphocytic leukaemia, Richter transformation of chronic lymphocytic leukaemia, Chronic myeloid leukaemia, chronic phase, Chronic myeloid leukaemia, accelerated and blast phase, Primary myelofibrosis, Standard-risk B-cell acute lymphoblastic leukaemia in children, High-risk acute lymphoblastic leukaemia in children (high-risk B-ALL and T-ALL), Philadelphia chromosome-positive acute lymphoblastic leukaemia in children (Ph-positive ALL), Philadelphia chromosome-like acute lymphoblastic leukaemia (Ph-like or BCR::ABL1-like ALL), Infant acute lymphoblastic leukaemia (KMT2A-rearranged, under one year), Relapsed and refractory acute lymphoblastic leukaemia in children, Acute myeloid leukaemia in children, Erdheim-Chester disease, Rosai-Dorfman-Destombes disease, Single-system Langerhans cell histiocytosis (bone, skin or one other organ), Multisystem Langerhans cell histiocytosis (with or without risk-organ involvement), Indolent and smouldering systemic mastocytosis, Advanced systemic mastocytosis (aggressive SM, SM with an associated haematological neoplasm, mast cell leukaemia), Early-stage classical Hodgkin lymphoma (stage I to II), Advanced-stage classical Hodgkin lymphoma (stage III to IV), Nodular lymphocyte-predominant Hodgkin lymphoma (nodular lymphocyte-predominant B-cell lymphoma), Relapsed and refractory classical Hodgkin lymphoma
The effusion is drained and sent, fresh, for cytology, flow cytometry and immunohistochemistry. The diagnosis requires the Kaposi sarcoma herpesvirus latency-associated nuclear antigen in the tumour nuclei. A cavity lymphoma without the virus is a different disease, recognised separately in 2022, that arises in fluid overload from heart failure, kidney failure or cirrhosis and behaves better. HIV testing is part of the work-up in every case.
Combination chemotherapy, with antiretroviral therapy started or optimised at the same time where there is HIV, because controlling the HIV is part of controlling the lymphoma. Anti-CD20 antibodies have no role: the cells do not carry CD20. There has never been a randomised trial in this entity and the regimens come from series and from the HIV-associated lymphoma literature; they sit in the treatment layer of this family and on the HIV-associated lymphoma page. Entry into a trial is a reasonable first choice rather than a last resort.
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Query for this cancer: (TITLE:"Primary effusion lymphoma" OR ABSTRACT:"Primary effusion lymphoma" OR TITLE:"PEL" OR ABSTRACT:"PEL" OR TITLE:"Body cavity-based lymphoma" OR ABSTRACT:"Body cavity-based lymphoma" OR TITLE:"Extracavitary primary effusion lymphoma" OR ABSTRACT:"Extracavitary primary effusion lymphoma" OR TITLE:"KSHV/HHV8-associated lymphoma" OR ABSTRACT:"KSHV/HHV8-associated lymphoma" OR TITLE:"HHV8-positive primary effusion lymphoma" OR ABSTRACT:"HHV8-positive primary effusion lymphoma") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Primary effusion lymphoma, not a curated reading list.
The virus discovered in Kaposi sarcoma the year before was found in a group of lymphomas that grew in body cavities without forming a mass, which defined the disease.
WHO-HAEM5 made fluid overload-associated large B-cell lymphoma a separate entity: the same presentation in an older person with heart, kidney or liver failure, without the virus, with a mature B-cell rather than plasmablastic phenotype, and with a better outlook.
Across 236 United States patients diagnosed between 2001 and 2021, five-year relative survival rose from 21 to 37 per cent and median overall survival from 4 to 12 months between the first and second halves of the period.
The targets of this cancer's medicines and the ones linked to it directly.
Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes.
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Bleeding that does not stop by itself, bleeding from more than one site, or new bruising in several places or one large area.
Cumulative dose: risk rises steeply above 400-550 mg/m² (see the anthracycline calculator).
Reduce to 75% for CrCl 15-50.
Reduce by 50% for bilirubin 20-50 µmol/L and 75% for 50-85 µmol/L.
Heart damage from cancer treatment: anthracyclines weaken the heart muscle permanently in a dose-related way, trastuzumab does so reversibly, and some kinase inhibitors raise blood pressure or disturb rhythm. Heart function (LVEF) is monitored by ultrasound during treatment.
Hodgkin lymphoma is usually cured, and the problems that follow arrive twenty and thirty years later: heart disease, an underactive thyroid, and second cancers, especially breast cancer in women irradiated to the chest when young. Most of them can be watched for.
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